The present invention relates, in general, to drive systems for moving a load along a curved track and, more particularly, the invention relates to sliding plug doors for transit type vehicles.
Sliding plug doors for transit vehicles require a drive system which can move the doors along curved paths. When such a door is in its closed position, it is substantially flush with the side wall of the vehicle. When it is opened, it initially moves outward and then moves longitudinally, along the wall, outside the vehicle. Such doors, generally, are guided in that curved motion by rollers engaging a curved track.
A drive for such a door system includes a motor connected to a power conversion unit which applies motive power in both the outward and longitudinal directions, so that the door travels along the curved track.
U.S. Pat. No. 5,893,236 Power Operator for Sliding Plug Doors teaches a door drive employing a planetary gear drive. The planetary gear drive is powered by an electric motor connected to the planetary gear drive. The output shaft of the planetary gear drive has a pinion gear which engages a gear on the drive screw which provides the longitudinal motion. The planetary output gear of the planetary gear drive is connected to a plug/unplug lever to provide motion in and out of the wall of the vehicle. When the door is in the closed position and is energized to open the door, power flows to the planetary output gear to move the door out of the wall of the vehicle. Then, as the door moves along the track, power flows to the drive screw which is connected to a door hanger to move the door longitudinally. It is noted that planetary gear drives are quite expensive.
Another approach to driving a plug door is to have a motor connected to power a drive screw which engages a drive nut which moves the door longitudinally. The motor is allowed to rotate due to the reaction torque due to driving the drive screw. Rotation of the motor is used to move the door into and out of the sidewall of the transit vehicle.
Yet another approach to driving a plug door is to have a curved track substantially coplanar with the straight track to move the door first along the curved path and then longitudinally. A drive for this system includes a motor indirectly connected to linear drive members through a set of well known spur gears. A drive pivot connected to a drive link design requires only the linear input and therefore does not require the use of a planetary gear.
The above applications utilize an electric motor as a primary drive mover. Generally electric prime movers requires a more precise control circuit for door motion control. It is noted that such a control circuit can be quite complex.
In one aspect, the present invention is a drive system for moving a load along a curved path. The drive system includes a base for mounting the drive system, the base having a curved track for guiding the load along the curved path. There is a load engaging mechanism mounted on the base for movement relative to the base for moving the load. This load engaging mechanism having a curved track engaging roller for engaging the curved track. A linear drive mechanism including a linearly driven member is mounted on the base. The linearly driven member includes a driving pivot. A drive link is attached to the driving pivot at a drive force receiving end of the drive link, the drive link including a driven pivot at a drive force communicating end of the drive link. The driven pivot is attached to the load engaging mechanism, whereby linear motion of the driving pivot causes motion of the load along the curved path.
In another aspect, the invention is a drive system for a plug door of a vehicle having a sidewall. The drive system moves the plug door along a curved path between a closed position substantially within the sidewall of the vehicle and an open position adjacent the sidewall of the vehicle. The drive system has a base for attachment to the vehicle and a carriage mounted on the base for movement in a transverse direction relative to the sidewall. There is at least one elongated support member mounted on the carriage substantially parallel to the sidewall. One or more hangers for supporting the plug doors are mounted on the elongated support member for movement thereon. A curved track is either mounted on the base or formed as a portion of the base. A curved track engaging roller is mounted on the hanger, the curved track engaging roller engaging the curved track. The drive system further includes a linear drive mechanism including a linearly driven member, the linearly driven member including a driving pivot. A drive link is attached to the driving pivot at a drive force receiving end of the drive link, the drive link having a driven pivot at a drive force communicating end of the drive link. The driven pivot is attached to the hanger, so that linear motion of the driving pivot causes motion of the door along the curved path so that the plug door moves between the closed position substantially within the sidewall of the vehicle and the open position adjacent the sidewall of the vehicle.
In another aspect, the invention is a drive system for a pair of biparting plug doors consisting of a first door and a second door. The biparting plug doors are for a vehicle having a sidewall. The drive system moves the first door along a first curved path between a first door closed position substantially within the sidewall of the vehicle and a first door open position adjacent the sidewall of the vehicle. The drive system simultaneously moves the second door between a second door closed position substantially within the sidewall of the vehicle and a second door open position adjacent the sidewall of the vehicle. The drive system includes a base for attachment to the vehicle and a carriage mounted on the base for movement in a transverse direction relative to the sidewall. There are also a first elongated support member and a second elongated support member mounted on the carriage substantially parallel to the sidewall. A first hanger for supporting the first door is mounted on the first elongated support member for movement thereon and a second hanger for supporting the second door is mounted on the second elongated support member for movement thereon. A curved track is either mounted on the base or formed as a portion of the base. A first curved track engaging roller is mounted on the first hanger, the first curved track engaging roller engaging the curved track. There is also a first linear drive mechanism including a first linearly driven member, the first linearly driven member including a first driving pivot. A first drive link is attached to the first driving pivot at a drive force receiving end of the first drive link, the first drive link having a first driven pivot at a drive force communicating end of the first drive link. The first driven pivot is attached to the first hanger so that linear motion of the first driving pivot causes motion of the first door along the first curved path, causing the first door to move between the first door closed position substantially within the sidewall of the vehicle and the first door open position adjacent the sidewall of the vehicle. There is also a second linear drive mechanism including a second linearly driven member, the second linearly driven member including a second driving pivot. A second drive link is attached to the second driving pivot at a drive force receiving end of the second drive link, the second drive link having a second driven pivot at a drive force communicating end of the second drive link. The second driven pivot is attached to the second hanger so that linear motion of the second driving pivot causes motion of the second door along the second curved path, causing the second door to move between the second door closed position substantially within the sidewall of the vehicle and the second door open position adjacent the sidewall of the vehicle.
It is, therefore, one of the primary objects of the present invention to provide a drive system for moving a load along a curved path.
Another object of the present invention is to provide a relatively simple and inexpensive drive system for moving a load along a curved path.
Still another object of the present invention is to provide a drive system for moving a load along a curved path which is highly reliable.
Yet another object of the present invention is to provide a drive system for a plug door in a sidewall of a vehicle, the drive system moving the door out of the sidewall and then along the sidewall of the vehicle.
A further object of the present invention is to provide a powered plug door for a vehicle which does not require a planetary gear drive.
It is an additional object of the present invention to provide a powered plug door for a vehicle which does not require the use of reaction torque on the motor.
Still yet another object of the present invention is to provide a plug door drive system in which outward and longitudinal movement is enabled by a linear drive mechanism and a simple pivoted link.
Yet still another object of the present invention is to provide a plug door drive system in which outward and longitudinal movement is enabled by a linear drive mechanism and a simple pivoted link, the link also serving as an overcenter lock.
A still further object of the present invention is to provide a plug door drive system having a drive screw in which bending moments in the drive screw are minimized.
An additional object of the present invention is to provide a drive system for biparting plug doors which employs linear drive mechanisms and simple pivoted links to provide outward and longitudinal movement of the doors.
Another object of the present invention is to provide a drive system for biparting plug doors which employs drive screws and simple pivoted links to provide outward and longitudinal movement of the doors.
In addition to the various objects and advantages of the present invention which have been generally described above, there will be various other objects and advantages of the invention that will become more readily apparent to those persons who are skilled in the relevant art from the following more detailed description of the invention, particularly, when the detailed description is taken in conjunction with the attached drawing figures and with the appended claims.